主要研究大口径KDP晶体的高强度三倍频性能。采用正交偏振干涉法测量了晶体的光轴均匀性分布，并在神光III原型装置上利用快速生长二倍频晶体开展了高强度三倍频实验，验证了折射率均匀性分布对三倍频效率和近场的影响。实验结果表明，大口径快速生长KDP晶体的三倍频性能基本上满足神光III装置的要求，但快速生长晶体的受激拉曼散射增益系数和激光损伤阈值等性能仍有待进一步考核。

The frequency conversion performance of a large scale rapid growth KDP crystal is studied. Using the orthogonal polarization interferometry (OPI) technique, the spatial refractive-index non-uniformities which prohibit the attainment of phase matching at all locations in the crystal is measured. Then third harmonic generation (THG) experiments with the large scale rapid growth KDP doubler on the prototype of SG-III laser facility to estimate the influence of refractive-index non-uniformities on conversion efficiency and 3ω beam near-field are conducted. According to the experimental results, this large scale rapid growth KDP crystal meets the basic requirements. But for specific applications, other aspects such as the stimulated Raman scattering gain coefficient and laser-induced damage threshold should be further considered.